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THE 


LATENT  TIME  OF  THE  KNEE-JERK 


BY 


E.  CAREY  APPLEGARTH,  B.  A.,  PH.  D.?  M.  D. 


A  THESIS 

PEESENTED   FOR  THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY   IN 
THE  JOHNS   HOPKINS  UNIVERSITY 


JUNE,  1890 


THE  FRIEDENWALD  CO.,  PRINTERS 
BALTIMORE 


THE 


LATENT  TIME  OF  THE  KNEE-JERK 


BY 

E.  CAREY  APPLEGARTH,  B.  A.,  PH.  D.,  M.  D. 


A  THESIS 

PRESENTED   FOB  THE   DEGREE   OF   DOCTOR  OF  PHILOSOPHY   IN 
THE  JOHNS   HOPKINS  UNIVERSITY 

JUNE,  1890 


THE  FR1EDENWALD  CO.,  PRINTERS 
BALTIMORE 


BIOLOGY 
LIBRARY 


UNIVERSITY 

OF 


THE  LATENT  TIME  OF  THE  KNEE-JERK. 


From  the  time  of  its  study  by  Westphal  and  Erb  in  1875  the 
knee-phenomenon  has  been  a  subject  of  increasing  interest  to  the 
physician,  to  'physiologists,  and  to  the  psychologist.  Its  clinical 
usefulness  has  been  especially  recognized  in  the  United  States  and 
has  led  to  numerous  investigations  intended  to  solve  questions  of 
special  interest  to  the  physician.  There  is,  perhaps,  no  other  sub- 
ject concerning  which  the  scientific  physician  has  during  late  years 
contributed  so  much  to  physiological  knowledge ;  nor  any  which 
so  well  illustrates  the  mutual  dependence  of  clinical  observation 
and  physiological  experiment. 

Most  of  the  work  in  this  line  of  inquiry  has  been  done  on  man, 
and  usually  with  the  aim  to  determine  the  absence,  presence,  or 
amount  of  the  knee-jerk  under  various  conditions,  normal  and 
pathological.  The  accurate  measurement  of  the  time  element  is 
extremely  difficult  in  human  beings,  and  our  knowledge  of  this 
element  still  far  from  satisfactory ;  this  fact  led  me  to  the  investi- 
gation now  described.  Without  attempting  here  an  exhaustive 
review  of  the  literature  bearing  upon  the  latent  time  of  the  knee- 
phenomenon  (or  knee-jerk  as  many  prefer  to  call  it),  a  brief 
account  of  previous  investigations  in  regard  to  the  time  involved 
will  be  useful. 

Tschirjew  l  in  1878  undertook  the  solution  of  the  problem  in 
the  following  way.  Over  the  ligamentum  patellae  was  bound  a 
piece  of  rubber  on  which  a  bit  of  thin  sheet  copper  was  fastened. 
A  conducting  wire  ran  from  this  plate  to  an  electric  signal  con- 
nected with  a  Daniell  cell.  From  the  same  battery  extended 
another  wire  to  the  metallic  end  of  a  percussion  hammer,  so  that 
at  the  delivery  of  the  tap  upon  the  ligament,  or  rather  upon  the 
copper  plate  over  the  latter,  the  current  was  closed  through  the 

1  Tschirjew,  Arch.  f.  Psych.  8,  1878,  p.  689. 


signal.  A  contact  key  placed  over  the  m.  quadriceps  femoris, 
on  contraction  of  the  muscle,  directed  a  current  from  another 
Daniell  cell  through  a  second  electric  signal.  Both  signals,  and  a 
Marey's  chronograph  making  one  hundred  double  vibrations  per 
second,  wrote  in  the  same  vertical  line  on  a  revolving  drum.  The 
signals  were  so  adjusted  that  their  respective  electrical  latent 
periods  were  equal.  For  the  results  obtained  by  Tschirjew  and 
others  see  table  I,  p.  6. 

In  the  succeeding  year  Gowers1  measured  the  knee-jerk  latency 
by  attaching  to  the  foot  a  pen  which  traced  the  movement  of  the 
foot  on  a  revolving  drum,  on  which  a  chronograph  pen  also 
wrote.  No  mention  is  made  of  the  manner  of  marking  the  instant 
of  the  tap  on  the  ligament.  Waller,2  in  1880,  caused  the  latent 
time  of  the  knee-jerk  to  be  "  recorded  by  a  lever-bearing  tympa- 
num, in  connection  with  an  explorer  fixed  on  the  muscle.  A  tube 
branching  off  the  tympanum  tube  and  crossing  the  tendon  was 
first  employed  to  record  percussion.  But  the  jar  communicated 
to  the  explorer  by  the  percussion  is  sufficient  to  record  its 
instant."  He  makes  use  of  a  revolving  drum,  the  quick  rate  of 
which  was  three  mm.  in  one  one-hundredth  of  a  second.  The 
time  tracing  was  effected  by  a  tuning  fork  making  one  hundred 
double  vibrations  per  second. 

Eulenburg 3  employed  the  vibrating  glass  plate  of  Landois,  and 
Brondgeest's  pansphygmograph  somewhat  modified.  The  tuning 
fork  being  struck,  in  the  same  vertical  line  upon  the  blackened 
plate,  so  set  in  motion,  two  levers  traced  out  their  respective 
curves,  being  governed  by  tambours  provided  with  90-96  cm. 
rubber  tubing  extending  to  two  receiving  tambours — one  on  the 
m.  quadriceps  femoris  and  the  other  upon  the  knee.  The  one 
fastened  on  the  thigh  was  an  ordinary  Upham's  cup,  4J  cm. 
diameter,  bounded  on  the  lower  side  by  an  elastic  membrane  with 
the  customary  button  for  resting  upon  the  muscle.  The  one 
strapped  around  the  knee,  however,  consisted  of  a  brass  ring,  3 
cm.  in  diameter,  over  the  upper  and  lower  surfaces  of  which  were 

1  Gowers,  Med.  Chir.  Transactions,  Vol.  LXII,  1879,  p.  269. 
8  Waller,  Brain,  July,  1880,  p.  179. 

5  Eulenburg,  Neurol.  Centralbl.  1,  1882,  S.  3;  and  Zeitschrift  f.  klinische 
Med.  4,  1882,  S.  179. 


tied  elastic  membranes.  In  an  experiment,  the  vibrating  glass 
being  set  in  motion  by  the  assistant,  the  ligamentum  patellae  of  the 
subject  is  struck  by  the  operator's  hand ;  the  wave  of  compression 
thus  originated  in  the  tambour  covering  the  knee  is  transmitted 
to  the  recording  tambour :  the  thickening  of  the  muscles,  which 
contract  to  produce  the  knee-jerk,  initiates  from  the  Upham's  cup 
a  similar  chain  of  events ;  and  the  latent  time  of  the  contraction 
may  at  once  be  read  off  in  swings  of  the  tuning  fork.  The  time 
(0.003")  taken  by  the  wave  to  traverse  the  tubing  connecting  the 
receiving  with  the  recording  tambours  is  eliminated  by  having 
the  same  length  of  tubing  in  each  case. 

Rosenheim1  attacked  the  problem  with  an  instrument  specially 
devised  for  the  purpose.  It  consists  of  two  uprights,  one  im- 
movably attached  near  its  upper  extremity  to  the  bottom  of  a 
V-shaped  collar,  and  the  other  mobile  around  a  Charnier's  joint  in 
the  two  arms  of  the  latter.  A  little  above  this  joint  there  is 
on  the  one  upright  a  plate  for  making  electrical  contact  with  a 
screw  carried  by  the  other.  The  uprights  may  be  adjusted  by 
means  of  a  spring  situated  below  the  joint.  On  the  lower  edge  of 
each  upright  is  a  ring,  to  which  is  secured  the  band  strapping  the 
instrument  to  the  leg.  When  the  muscle  contracts,  contact  is 
broken  between  the  screw  and  the  corresponding  plate,  and  an 
electric  signal  marks  this  instant  on  a  revolving  drum,  whose 
quick  rate  equals  one  metre  of  paper  in  thirteen  seconds.  The 
tap  upon  the  patella  is  registered  by  another  signal,  the  action  of 
which  depends  upon  a  blow  from  a  percussion  hammer  in  connec- 
tion with  a  Daniell  cell,  upon  a  piece  of  copper  or  tin  foil,  also  in 
connection  with  the  battery,  and  placed  over  the  ligament. 

The  results  of  these  investigators  along  with  those  of  A.  de 
Watteville,2  who  availed  himself  of  Waller's  method,  and  those 
of  Brissaud,3  who  used  an  electric  signal  for  recording  the  tap, 
and  a  Mendelssohn's  myograph  to  record  the  contraction  of  the 
muscle,  may  be  tabulated  as  follows : 

'Rosenheim,  Arch.  f.  Psychiatrie,  XIV,  1884,  S.  184. 

2A.  de  Watteville,  Brain,  July,  1882,  Vol.  5,  p.  287. 

8  Brissaud,  Publications  du  Progres  Med.,  Paris,  1880,  p.  206. 


TABLE  I. 

Subjects. 


2  patients. 

f  2  normal  persons.  1 

\  1  case  of  lateral  sclerosis.  J 
12  patients. 

f  ?  normal.         1 

\  ?  hemiplegia.  j 
100  students. 
1  patient. 

f  4  individuals. 

J  cases  of  hemiplegia. 

!  10  rabbits 


Observations. 
146 

Latency. 
0.0595" 

9 

0.100 

? 

0.035 

J 

0.050 
0.015 

? 

0.024 

9 

0.025 

? 
9 

? 
V 

0.04313 
0.025 
0.033 
0.023 

Worker. 
Tschirjew, 

Gowers, 
Waller,1 
Brissaud, 

Eulenburg, 

A.  de  Watteville, 

Rosenheim, 


With  the  exception  of  that  of  Gowers,  it  will  be  seen  that  in  all 
the  above  contributions  to  the  literature  of  the  subject  in  hand, 
the  contraction  of  the  m.  quadriceps  femoris  has  been  recorded  by 
implements  which  depend  for  their  efficiency  upon  the  swelling  of 
the  muscle  as  it  contracts.  Remembering  how  difficult  it  is,  even 
with  an  isolated  muscle,  to  obtain  apparatus  sufficiently  delicate 
to  render  manifest  the  initial  stage  of  contraction,  and  having  in 
mind  the  importance  of  the  question  as  to  whether  the  knee  phe- 
nomenon is  or  is  not  a  reflex  action,  it  seemed  desirable  to  make 
further  experiments  with  more  accurate  methods. 

I  have  chosen  dogs  as  the  subjects  of  my  research.  In  a  later 
paper  I  hope  to  discuss  the  matter  more  fully  and  to  give  obser- 
vations on  the  human  subject. 

In  the  present  investigation  five  hundred  and  eighty  experi- 
ments were  made  on  thirty-two  dates  upon  three  bitches,  which  for 
the  sake  of  convenience  may  be  designated  A,  B,  C.  Of  these 
experiments,  one  hundred  and  one  were  performed-  upon  A,  two 
hundred  and  ninety-one  on  B,  and  one  hundred  and  eighty- 
eight  on  C.  A  and  B  had  their  spinal  cords  severed  at  the  level 
of  the  last  dorsal  vertebra,  C  was  normal.  All  three  were  small 
and  as  similar  as  it  was  possible  to  obtain  them. 

1  Since  writing  the  above  I  notice  Waller  has  published  a  more  recent  research 
in  the  Journal  of  Physiology,  Vol.  XI,  p.  384.  With  improved  apparatus  he 
finds  that  0.012"  intervenes  between  the  instant  of  percussion  upon  a  rabbit's 
tendon  and  the  resulting  muscular  contraction.  Deducting  0.005/x  for  the 
mechanical  lost  time,  and  adding  0.001"  to  counterbalance  the  lost  time  of  the 
Despretz  signal,  he  obtains  the  corrected  interval  0.008". 


A  was  operated  upon  with  aseptic  precautions  during  the  first 
week  of  April,  1889.  She  recovered  well  and  remained  strong 
and  healthy ;  but  owing  to  other  duties  it  was  impossible  for  me 
to  experiment  upon  her  knee-jerk  until  the  following  January. 
Towards  the  latter  part  of  February  ^1890),  in  consequence  of  an 
attack  of  mange,  a  lotion  was  applied  to  her  skin,  which  she  licked 
off,  poisoning  herself.  The  autopsy,  made  with  the  kind  assist- 
ance of  Dr.  W.  T.  Councilman  of  the  Johns  Hopkins  Hospital, 
showed  the  severed  spinal  cord  was  reunited  by  dense  fibrous 
tissue.  Beyond  obvious  degeneration  of  certain  nerve  tracts 
(which  had  been  going  on  for  eleven  months  prior  to  death)  no 
pathological  change  was  manifest  in  the  spinal  cord.  The  whole 
cerebro-spinal  axis  was  carefully  preserved  for  future  microscopi- 
cal examination. 

As  the  cord  of  A  was  cut  above  the  centres  of  defecation  and 
micturition,  there  "was  no  a  priori  reason  why  these  natural 
actions  should  not  be  reflexly  excited,  and  this  conclusion  was 
amply  justified  by  the  facts.  As  Goltz  found,  sponging  the  anus, 
pinching  the  tail,  and  even  the  dragging  of  the  hinder  parts  about 
by  the  animal  itself  while  it  crawled  on  its  fore  limbs,  proved 
effectual  in  leading  to  evacuation  of  the  bladder  and  rectum. 
Whenever  micturition  or  defecation  occurred  there  was  an  accom- 
panying train  of  reflexes  involving  the  muscles  of  the  tail  and 
hind  legs. 

The  animal  was  fed  and  exercised  with  great  regularity.  Her 
exercise  consisted  in  permitting  her,  while  I  supported  her  hind 
limbs  off  the  floor,  to  run  or  walk  where  and  how  she  liked  for 
fifteen  to  thirty  minutes  in  the  morning,  the  same  at  noon,  and 
one-half  to  one  hour  at  night.  She  was  always  at  liberty,  when 
not  at  exercise,  and  could  crawl  around  as  much  as  she  pleased. 
In  addition  the  muscles  of  the  paralysed  legs  were  exercised  by 
electric  stimuli,  and  from  the  date  on  which  the  knee-jerk  obser- 
vations commenced  almost  daily  experimentation  added  its  quota 
towards  keeping  the  muscles  in  healthy  condition.  The  expendi- 
ture of  time  and  energy  involved  in  caring  for  this  animal 
during  so  many  months  was  very  great,  but  in  no  other  way  can 
good  health  be  secured  to  a  dog  with  severed  spinal  cord,  and 


8 

the  good  health  of  the  animal's  muscles  and  nerves  was  essential 
to  me. 

B  was  operated  upon  the  day  following  the  death  of  A,  and 
was  used  for  experimentation  upon  her  knee-jerk  two  weeks  later. 
Her  health  remained  good.  The  same  care  was  taken  as  with  A. 

C,  as  stated  above,  was  normal,  and  as  far  as  possible  kept 
under  the  same  conditions  as  were  A  and  B. 

All  three  dogs  were  young,  and  were  taught  without  much 
difficulty  to  lie  quiet  when  experimented  on. 

A  thin  cushion  placed  on  a  board  formed  a  bed.  From  one  side 
of  the  boards  two  straps  extended.  One  strap  passed  over  the 
neck  and  the  other  over  the  body  just  posterior  to  the  forelegs. 
This  bed  was  not  disagreeable ;  indeed,  the  dogs  appeared  to  find 
it  comfortable,  since  they  would  often  go  to  sleep  on  it. 

While  the  trunk  was  thus  kept  quiet  the  leg  (in  all  cases  the 
right)  whose  knee-jerk  was  to  be  investigated  was  held  in  a  large 
retort-holder  which  could  be  adjusted  to  fit  snugly,  binding  upon 
the  condyles  of  the  femur  with  pressure  just  sufficient  to  hold  the 
leg  securely.  The  upright  carrying  this  holder  was  clamped  to 
the  table,  so  that  the  only  movement  that  could  take  place,  when 
the  ligamentum  patellae  was  struck,  was  that  of  the  tibia  on  the 
knee-joint.  The  foot  was  strapped  in  two  places,  not  too  firmly, 
to  a  splint  extending  from  the  toes  to  a  point  a  little  past  the 
tarsus. 

This  splint  is  of  wood  one  inch  thick,  three  long,  one  broad, 
and  has  its  upper  surface  concave.  At  each  end  there  are  two 
buttons,  one  on  each  side,  for  leather  straps  hanging  from  a  hook 
which  swings  in  an  iron  thimble  at  the  end  of  a  cord  suspended 
from  the  ceiling.  At  the  distal  end  of  the  splint  is  a  binding 
screw,  into  the  top  of  which  is  soldered  a  stiff  platinum  wire.  The 
latter  may  be  made  to  press  against  a  contact  plate  of  platinum 
that  is  fastened  upon  a  block  of  vulcanite,  which  in  turn  slides 
upon  an  upright  similar  to  that  of  a  Roy's  universal  holder.  A 
Pfeil  signal  is  included  in  this  circuit. 

Over  the  ligamentum  patellae  was  attached,  by  means  of  adhe- 
sive plaster,  a  thin  narrow  strip  of  brass  covered  with  platinum. 
Upon  this  strip  of  brass,  which  also  stands  in  electrical  connection 
with  a  Pfeil  signal,  impinges  a  hammer  the  exact  duplicate  of 


9 

Lombard's,1  with  the  exception  that  the  head  is  very  much  lighter, 
weighing  only  ten  grams,  and  is  insulated  from  the  handle,  and 
that  instead  of  the  catch  holding  the  head  up  is  an  electro-magnet 
performing  the  same  office.  This  hammer,  being  in  the  same 
circuit  as  the  strip  of  brass  fitting  snugly  over  the  knee,  causes, 
when  it  strikes  the  latter,  a  closure  of  the  current,  which  instant 
the  signal  records.  The  contact  edge  of  the  head  of  the 
hammer  is  covered  with  platinum,  as  in  all  other  cases  where 
instantaneous  electrical  connection  was  desired.  Throughout  the 
whole  research  a  very  light  tap  was  used,  due  to  a  fall  of  the  ham- 
mer of  two  degrees  of  the  circle. 

The  exact  arrangement  of  these  various  parts  can  best  be  under- 
stood by  reference  to  the  diagram  represented  in  Fig.  3,  Plate 
XL  B  is  a  battery  of  two  large  Daniell  cells,  while  T  is  a  break 
mechanism  or  trigger  like  that  of  a  pendulum  myograph.  When 
T  is  up  against  the  screw,  and  H  is  not  touching  jfiT,  the  current 
finds  a  complete  circuit  through  the  electro-magnet  M  back  to  the 
battery.  When,  however,  the  trigger  is  down,  as  shown  in  the 
diagram,  the  current  can  no  longer  flow  through  M,  but  is  com- 
pelled to  pass  through  H,  the  hammer,  K,  the  knee  piece,  8,  the 
signal,  and  thence  back  to  the  battery.  But  this  circuit  is  only 
closed  when  H  touches  K. 

Fig.  2,  Plate  XI,  shows  in  a  diagrammatic  way  the  circuit  of 
the  other  signal.  B  is  a  battery  of  one  large  Daniell  cell.  P  is 
the  stiff  platinum  wire  making  contact  with  (?.  When  P  is  press- 
ing upon  C  the  current  flows  from  the  battery  to  P,  through  the 
contact  plate  C  and  back  to  the  battery.  When,  however,  con- 
tact is  broken  between  P  and  C  the  current  must  pass  through 
wr,  which  is  of  very  fine  wire,  to  the  signal  8,  and  back  to  the 
battery.  K  is  simply  a  key  which  opens  this  circuit  when 
desired. 

The  signals,  as  mentioned  above,  are  of  the  same  make ;  they 
write  in  the  same  vertical  line  on  the  smoked  glass  plate  of  the 
pendulum  myograph  described  by  Sewall,2  and  are  placed  upon  a 
supporting  table  which  can  be  screwed  up  until  the  writing  points 
of  the  levers  just  touch  the  blackened  plate.  The  latent  period 

1  Lombard,  Amer.  Journal  of  Psychology,  Vol.  I,  1887,  p.  5. 
8  Sewall,  Jour.  Physiol.,  Vol.  II,  p.  164. 


10 

of  each  was  carefully  traced  on  the  myograph  plate,  which  for  the 
purpose  was  made  to  swing  through  an  arc  of  displacement 
646.8  mm.,  with  therefore  a  velocity  of  1  mm.  in  0.000492"  as  it 
passes  the  writing  point  of  the  signal.  The  difference  in  the  time 
equivalents  of  the  signals  was  found  to  be  0.00008". 

After  trying  fish-bones,  glass  drawn  out  to  a  very  fine  point 
and  other  objects,  I  finally  decided  on  exceedingly  delicate  cambric 
needles  as  most  satisfactory  for  the  writing  points. 

The  pendulum  myograph  in  use  in  our  laboratory  beats  true 
seconds,  and  swung,  in  the  present  inquiry,  through  an  arc  of 
displacement  of  220  mm.  Consequently  if  v  equals  the  velocity 
of  the  centre  of  the  plate  as  it  passes  the  zero  point  of  fixed 
scale  corresponding  to  the  middle  of  the  swing  of  the  pen- 
dulum, ch  the  chord  of  the  arc  of  displacement  of  the  centre  of 
gravity  of  the  pendulum,  g  the  intensity  of  gravity,  and  I  the 
length  of  a  second's  pendulum  at  the  place  in  question,  then  the 
formula 


i 

gives  at  once  the  desired  information.  In  this  way  the  rate  was 
calculated  to  be  1  mm.  in  0.001446."  As  a  matter  of  fact  it  was 
found  that  this  rate  did  not  measurably  vary  for  the  first  two  cen- 
timeters on  each  side  of  the  central  line  of  the  plate,  but  neverthe- 
less a  tuning  fork  making  200  double  vibrations  per  second  was 
from  time  to  time  employed  as  a  control. 

The  actual  order  of  each  experiment  has  been  as  follows  :  The 
dog  having  been  placed  on  the  bed,  its  leg  is  clamped  at  the  knee 
and  its  foot  strapped  to  the  splint.  After  the  foot  has  come  to  its 
position  of  rest,  the  contact  plate  (7,  Fig.  2,  Plate  XI,  is  pushed  up 
against  the  stiff  wire  P  on  the  splint  until  the  foot  is  moved 
forward  about  an  inch,  so  that  considerable  pressure  is  thereby 
exerted  by  the  wire  upon  the  contact  plate.  When  so  arranged, 
moderate  blows  on  the  splint  and  distal  portion  of  the  tibia  prove 
ineffectual  in  breaking  contact.  When,  however,  the  hammer 
excites  the  knee-jerk  by  striking  on  the  ligamentum  patella?,  con- 
tact is  broken  and  the  latency  of  the  phenomenon  is  registered. 

I  hoped  by  thus  taking  advantage  of  the  great  leverage  of  the 
extensors  of  the  crus  to  be  able  to  obtain  the  record  of  an  early,  if 
not  the  earliest,  stage  of  contraction. 


11 

The  trigger  T,  Fig.  1,  Plate  XI,  slides  upon  the  metal  micro- 
meter scale  of  the  myograph,  and  is  so  placed  that  when  the  latter 
in  its  swing  knocks  it,  the  signal  marks  near  the  middle  of  the 
plate  the  instant  of  the  ensuing  tap  upon  the  tendon.  This  posi- 
tion having  been  secured,  all  is  ready  for  an  experiment. 

The  following  tables  give  details  of  a  few  of  the  experiments 
performed  in  this  way.  jRx  — R  2  represents  the  distance  expressed 
in  mm.  from  the  beginning  of  the  tracing  of  one  signal  to  the  like 
point  of  the  other's  tracing.  The  second  column  contains  the  time 
equivalents  of  the  given  number  of  mm.  (—mm.  X  0.001446"), 
and  the  third  column  the  equivalents  corrected  for  difference  in 
latency  of  the  two  signals  (=z[mm.  X  0.001446"]  +  0.00008"). 

TABLE  II. 

Jan.  30, 1890.  Bitch  A.  Cloudy.  External  temperature  9°  C. 
Room  temperature  20°  C.  Dog  exercised  but  not  fed.  Began 
9.30  A.  M.  Observations  made  every  minute. 

fit -it* 

5.3 

7.2 
9.0 
7.2 
7.8 
7.1 
8.4 
7.3 
9.0 
5.7 
8.8 
6.4 
5.8 
8.8 
6.1 


TABLE  III. 

March  25,  1890.  B.  Cloudy.  External  temperature  3.5°  C. 
Room  temperature  25°  C.  Dog  exercised  but  not  fed.  Began 
9.15  A.  M.  Observations  made  every  minute. 


Time. 

Corrected  Time. 

0.00766" 

0.00774" 

0.01041 

0.01049 

0.01301 

0.01309 

0.01041 

0.01049 

0.01128 

0.01136 

0.01027 

0.01035 

0.01215 

0.01223 

0.01056 

0.01064 

0.01301 

0.01309 

0.00824 

0.00832 

0.01272 

0.01280 

0.00925 

0.00933 

0.00839 

0.00847 

0.01272 

0.01280 

0.00882 

0.00890 

Average, 

0.01060" 

Corrected  average, 

0.01068" 

12 


9.5 
6.5 

7.8 
7.2 
7.9 
6.0 
9.8 
8.2 
9.4 
8.8 
7.9 
7.4 
7.5 
6.8 
6.1 
6.8 
6.4 
8.2 
6.1 


Time. 
0.01374' 
0.00940 
0.01128 
0.01041 
0.01142 
0.00868 
0.01417 
0.01186 
0.01359 
0.01272 
0.01142 
0.01070 
0.01085 
0.00983 
0.00882 
0.00983 
0.00925 
0.01186 
0.00882 
Average, 


Corrected  Time. 
0.01382" 
0.00948 
0.01136 
0.01049 
0.01150 
0.00876 
0.01425 
0.01194 
0.01367 
0.01280 
0.01150 
0.01078 
0.01093 
0.00991 
0.00890 
0.00991 
0.00933 
0.01194 
0.00890 


Corrected  average,  0.01106" 


TABLE  IV. 

March  24.  C.  Clear.  External  temperature  6°  C.  Room 
temperature  23°  C.  Dog  exercised  but  not  fed.  Began  12  M. 
Observations  made  every  minute. 


7.2 
6.9 
9.0 
9.8 
9.1 
9.6 

10.4 
8.9 
9.5 
8.8 

10.1 
8.0 
9.2 

10.2 
8.3 

10.5 
9.2 
9.5 


Time. 
0.01041' 
0.00998 
0.01301 
0.01417 
0.01316 
0.01388 
0.01504 
0.01287 
0.01374 
0.01272 
0.01460 
0.01158 
0.01330 
0.01475 
0.01200 
0.01518 
0.01330 
0.01374 
Average, 


Corrected  Time. 
0.01049" 
0.01006 
0.01309 
0.01525 
0.01324 
0.01396 
0.01512 
0.01295 
0.01382 
0.01280 
0.01468 
0.01166 
0.01338 
0.01483 
0.01208 
0.01526 
0.01338 
0.01382 


0.01320" 


Corrected  average,  0.01328' 


13 


After  doing  a  number  of  experiments  in  this  way  it  occurred 
to  me  to  test  these  results  by  causing  the  knee-jerk  to  make 
contact.  Of  course  some  time  must  be  lost  hereby,  but  neverthe- 
less the  averages  should  be  approximately  equal,  caeteris  paribus. 
The  only  change  in  the  apparatus  necessary  for  this  purpose  was 
to  dispense  with  the  resistance  circuit  wr,  Fig.  2,  and  put  the 
signal  in  the  primary  circuit.  Now  the  contact  plate  (7,  Fig. 
2,  is  placed  in  front  of  P  at  a  distance  of  1  mm.,  and  an  upright 
is  clamped  to  the  table  back  of  the  splint,  so  that  the  leg  may 
have  exactly  the  same  amount  of  flexion  at  the  beginning  of 
each  experiment.  The  following  tables  give  a  few  of  the  protocols 
so  obtained. 

TABLE  V. 

March  19,  1890.  B.  Cloudy.  External  temperature  5°  C. 
Room  temperature  22°  C.  Began  10  A.  M.  Observations  every 
minute. 


R.-R,. 

9.8 


9.2 
9.5 

10.5 
5.0 
8.0 
5.2 
6.1 
8.8 

12.5 
9.0 
5.0 
5.8 
7.6 
8.0 

10.2 


Time. 

Corrected  Time. 

0.01417" 

0.01425" 

0.01388 

0.01396 

0.01330 

0.01338 

0.01374 

0.01382 

0.01518 

0.01526 

0.00723 

0.00781 

0.01157 

0.01165 

0.00752 

0.00760 

0.00882 

0.00890 

0.01272 

0.01280 

0.01806 

0.01814 

0.01301 

0.01309 

0.00723 

0.00731 

0.00839 

0.00847 

0.01099 

0.01107 

0.01157 

0.01165 

0.01475 

0.01483 

Average, 

0,01189" 

Corrected  average, 

0.01197" 

March  20,  1890.     C.     Cloudy. 
Room  temperature  22°  C.     Began  2  P.  M. 
minute. 


TABLE  VI. 

External  temperature  7°  C. 
Observations  every 


u 

JR,— R,.  Time.  Corrected  Time. 

17.5  0.02521"  0.02529" 

10.6  0.01533  0.01541 
12.0  9.01735                                0.01743 
13.0  0.01880  0.01888 

9.0                                0.01301  0.01309 

8.8                                0.01272  0.01280 

8.5                                0.01230  0.01238 

9.8                                0.01417  0.01425 

13.6                                0.01967  0.01975 

11.0                                0.01590  0.01598 

16.5                                0.02386  0.02394 

Average,  0.01712" 

Corrected  average,  0.01720" 

Desiring  now  to  apply  the  method  depending  upon  the  thick- 
ening of  the  muscle  as  it  contracts,  a  piece  of  brass  three  mm. 
square  was  bound  over  the  m.  quadriceps  femoris  by  an  elastic 
band.  Soldered  to  this  plate  were  a  copper  wire,  leading  to  the 
battery,  and  a  stiff  platinum  wire,  extending  vertically  upwards. 
Near  its  free  end  the  latter  was  bent  at  right  angles,  and  by  means 
of  a  micrometer  screw  a  sliding  stage  could  be  raised  up  under 
the  horizontal  arm  until  firm  yet  delicate  contact  was  made.  The 
connections  with  the  stage  working  on  the  micrometer  screw 
were  the  same  as  with  P,  Fig.  2,  so  that,  as  soon  as  the  muscle 
contracted,  the  circuit  was  opened  and  the  signal  recorded. 
Moderate  shocks  on  the  splint  and  body  did  not  suffice  to  break 
contact. 

The  following  are  some  of  the  results  furnished  by  this 
method. 

TABLE  VII. 

March  21,  1890.  B.  Cloudy.  External  temperature  12°  C. 
Room  temperature  22°  C.  Fed  at  2  P.  M.  Began  5  P.  M. 
Observations  half  a  minute  apart. 

s 

RJ—RI.  Time.  Corrected  Time. 

12.5  0.01808"  0.01826" 

11.8  0.01706  0.01714 

6.4  0.00925  0.00933 
7.0  0.01012  0.01020 

7.5  0.01085  0.01093 
7.2  0.01041  0.01049 

14.9  0.02155  0.02163 


15 


11.5 

8.8 

9.2 

8.8 

16.0 

12.4 

9.5 

9.8 

9.6 

10.2 

11.1 

10.2 

10.5 

10.1 

11.0 

13.5 

9.1 

10.0 

9.2 

9.9 

10.5 

6.5 

8.8 

9.6 

7.6 

9.0 

9.5 

10.2 

9.8 


Time. 
0.01663" 
0.01272 
0.01330 
0.01272 
0.02314 
0.01793 
0.01374 
0.01417 
0.01388 
0.01475 
0.01605 
0.01475 
0.01518 
0.01460 
0.01591 
0.01952 
0.01316 
0.01446 
0.01330 
0.01432 
0.01518 
0.00940 
0.01272 
0.01388 
0.01099 
0.01301 
0.01374 
0.01475 
0.01417 
Average, 


Corrected  Time. 
0.01671" 
0.01280 
0.01338 
0.01280 
0.02322 
0.01801 
0.01382 
0.01425 
0.01396 
0.01483 
0.01613 
0.01483 
0.01526 
0.01468 
0.01599 
0.01960 
0.01324 
0.01454 
0.01338 
0.01440 
0.01526 
0.00948 
0.001280 
0.01396 
0.01107 
0.01309 
0.01382 
0.01483 
0.01425 


0.01443' 


Corrected  average,  0.01451' 


TABLE  VIII. 


March  22,  1890.  C.  Rain.  External  temperature  10°  C. 
Room  temperature  22°  C.  Fed  12  M.  Began  5.30  P.  M. 
Observations  every  minute. 


R.-R,. 
10.4 
14.6 
13.5 
15.2 
9.0 
15.5 
16.8 
13.0 


Time. 
0.01504" 
0.02111 
0.01952 
0.02298 
0.01301 
0.02241 
0.02429 
0.01880 


Corrected  Time. 
0.01512" 
0.02119 
0.01960 
0.02306 
0.01309 
0.02249 
0.02437 
0.01888 


16 

flj— J?,.  Time.  Corrected  Time. 

14.8  0.02140"  0.02148" 

15.0  0.02169  0.02177 

9.9  0.01432  0.01440 

13.0  0.01880  0.01888 

13.3  0.01923  0.01931 

14.2  0.02053  002061 

11.2  0.01620  0.01628 

Average,  0.01928" 

Corrected  average,  0.01936" 

The  results  by  averages  of  all  the  experiments  by  each  method 
may  be  tabulated  as  follows :  By  the  first  method  where  the 
knee-jerk  caused  interruption  of  the  electric  current  the  average 
latent  time  in  case  of  A  and  B  was. 0.01  0",  while  with  C  it  was 
0.014.  By  the  second  method  above  given  the  average  for  B  was 
0.015",  while  for  C  0.02.  By  the  third  method  where  the  regis- 
tration of  the  signals  depended  upon  the  thickening  of  the  muscles, 
the  average  latent  time  for  Bwas  0. 016",  while  for  C  it  was  0.020. 

From  a  comparison  of  these  results  it  seems  probable  that  the 
latency  of  the  knee-jerk  of  the  dog,  as  obtained  by  the  electrical 
method,  is  not  over  0.014"-0.020". 

In  applying  the  second  method,  as  above  given,  it  was  frequently 
noticed  that  if  the  distance  between  (7  and  P,  Fig.  2,  Plate  XI, 
was  over  1  mm.,  say  1 J-2  mm.,  the  corresponding  difference  in 
time  became  excessively  disproportionate,  in  fact  almost  equiva- 
lent to  the  time  of  a  superficial  reflex.  The  following  table  will 
illustrate  this. 

TABLE  IX. 

March  20,  1890.  C.  Cloudy.  External  temperature  5°  C. 
Room  temperature  22°  C.  Exercised  and  fed.  Began  2  P.  M. 
Observations  made  every  minute.  Distance  of  C  from  P  2  mm. 

B,—  R-t.                                   Time.  Corrected  Time. 

34.9                                0.05047"  0.05055" 

33.6                                0.04867  0.04875 

40.9                                0.05914  0.05922 

42.8                                0.06189  0.06197 

38.2                                0.05522  0.05530 

43.2                                0.06247  0.06255 

41.0                                0.05929  0.05937 

41.4                                0.05986  0.05994 

40.2                                0.05813  0.05821 

Average,  0.05724" 

Corrected  average,  0.05732" 


THE  LA  TENT  TIME  OF  THE  KNEE-JERK.          17 

whereas,  the  average  of  a  number  of  time  measurements  of  skin 
reflexes  elicited  by  electrical  stimulation  applied  to  the  toe  of  A 
was  0.07141".  This  at  once  reminds  us  of  what  Gowers  observed, 
namely,  that  when  the  ligamentum  patellae  was  struck  the  curve 
traced  by  the  foot  left  the  abscissa  very  soon,  but  the  true  con- 
traction of  the  muscle  followed  at  a  somewhat  later  period. 

It  will  be  seen  also  that  by  each  method  the  latency  of  the  knee- 
jerk  is  less  in  the  dogs  with  their  spinal  cords  cut  than  in  the 
normal  one.  This  is  in  keeping  with  results  previously  obtained, 
and  tends  to  confirm  the  view  that  the  brain  is  one  of  the  impor- 
tant factors  concerned  in  the  time  of  the  phenomenon. 

Lombard  found  the  extent  of  the  knee-jerk  was  very  profoundly 
influenced  by  the  emotions,  variations  of  weather  and  the  like, 
and  it  seemed  of  interest  to  me  whether  such  changes  involved 
corresponding  differences  in  the  time.  In  this  respect,  however, 
my  results  were  not  quite  satisfactory,  and  after  the  first  few 
experiments  it  appeared  best  to  defer  this  matter  for  the  present. 

In  conclusion,  I  desire  to  acknowledge  my  obligations  to  Pro- 
fessor H.  Newell  Martin  for  his  kindness  and  valuable  sug- 
gestions. 


VITA. 

E.  C.  Applegarth  was  born  in  Baltimore,  March  28,  1866. 
After  passing  through  the  public  schools  of  that  city,  he  entered 
the  Johns  Hopkins  University  in  1884,  became  an  Honorary 
Scholar  the  same  year,  was  reappointed  each  of  the  two  sessions 
immediately  following,  and  received  his  degree  of  Bachelor  of 
Arts  in  1887.  On  graduation  he  was  awarded  a  university 
scholarship,  and  in  June,  1889,  was  appointed  a  Fellow  in  Biology. 


STUD.    FROM    BIOL.   LAB. 


VOL  V.     PLATE  XI, 


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